Arc-lamp.



C. P. STEINMETZ.

ARC LAMP.

APPLICATION FILED 0013.

Patented Oct. 3, 1916.

3 SHEETS-SHEET 1 C. P. STEINMETZ.

ARC LAMP.

APPLICATION FILED OCT. 3,1912.

Patented Oct. 3,1916.

3 SHEETS-SHEET 2 Inventor: Charles P. Steinmetz,

i l A 6 adefbcghmnfklo Fig. 3

His fittorney.

' c. P. STEINMETZ.

ARC LAMP.

APPLICATION FILED ocT. 3. 19|2.

Patented Oct. 3,1916.

3 SHEETS-SHEET 3 Witnesses:

m ma ut n5 P m a UNITED STATES PATENT OFFICE.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ARC-LAMP.

Patented. Oct. 3, 1916.

Application filed October 3, 1912. Serial N 0. 723,701.

T 0 all whom it may concern Be it known that 1, CHARLES P. STEIN- unrz, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Are- Lamps, of which the following is a specification.

My invention relates to are lamps and has particular reference to alternating current are lamps.

The objects of my invention are to provide an improved method of and apparatus for operating arc lamps on an alternating current system.

The novel features which I believe to be characteristic of my invention will be definitely indicated in the claims appended hereto.

The method of operation and the features of construction will be understood by reference to the following description taken in connection with the accompanying drawings, which show the preferred embodiments of my invention and in which Figure l is a skeleton view of a lamp embodying one form of my invention; Fig. 2 is a similar view showing the preferred form of my invention; Fig. 3 is a diagrammatic view of the device employed in the construction shown in Fig. 2 for diverting energy to the lamp circuit; Fig. 4 is a further modification of my invention; Fig. 5 is a graphic representation of the open circuit reactions taking place within the energy diverting device of Fig. 2; and Fig. 6 is a curve of arc resistance fluctuations, such as occur in an arc, of a character that may be advantageously produced in a lamp embodying my invention.

One well known method of operating arc lamps consists in extinguishing and immediately reestablishing the are when the arcresistance attains a predetermined value.

By this method of operation-the arc elec-,

trodes are brought intocontact with one another when such .predetermlned arc-resistanceexists, andare immediately separated a fixed and definite distance toagain strike.

the arc. This. operation of extinguishing the arc andsubsequent and immediate separationof the electrodes to, again establish the arois in rmittently repeated.-= I. have,- discovered that an arc lamp supplied with alternating current from an inductive device such as a simple inductive winding or an auto-transformer, as a local source of energy, can be very efficiently and satisfao tor ly operated by this method if the magnetic characteristics of the local source of energy supply are designed with particular reference to the arc to be produced.

In carrying my invention into effect I make use of a local inductive device which in a certain sense may be looked upon as a source of electrical energy which'is designed to divert to the arc lamp circuit a limited amount of energy. This limited amount of energy is determined with reference to the particular are to be produced, and corresponds to the normal energy requirements of the lamp, that is, to the maximum amount of energy which may be required to sustain the arc in normal operation as a stable alternating arc. The apparatus is so designed that when the arc-resistance between the electrodes rises suflicientlyto raise the energy requirement of the lamp circuit above the limited amount which the local source can divert or supply, the arc collapses and the electrodes come into engagement. A.

suitable mechanism, controlled by a current responsive device in the lamp circuit, then separates the electrodes a fixed distance.

My invention will be most readily understood by reference to Fig. 1 of the drawings. In this figure, the upper and lower elec trodes of the lamp are represented by reference numerals 1 and 2, respectively. The lower electrode is carried by a rod 3. which is suitably guidedin its movement in the lamp end is provided at its bottom with an arm 4, having a socket 5 at its outerendin which the lowerelectrode is received. The upper electrode 1 is connected to the rod 3 by a chain 6, or otherflexible connection,

passing over a pulley-7 pivoted at. 7 The upperelectrodeis received within a. carbonholder 8 insulated from the flexible member 6 and the frame of the lamp bywinsulating' brought into engagement bygravity. I? The electrodes are separated and-the arc established by a series magnet 10, having gang trode. The rod 12 pivotally engages a slot 14 of a lever 14, and thelever is pivoted at armature 11,.wh-ichisconnected by a rodl2l:

toaclntch 13which engages th l ppereleo 14 to a stationary part 15 of the lamp. The outer end of the lever 14 is pivoted at 14 to the stem of a dash-pot 16 of ordinary construction.

The lamp circuit, which includes the electrodes l and 2, and the series magnet 10, is supplied with alternating current from a local sourceof energy comprising an inductive device such as an inductive winding interposed between the conductors 17 and 18 of a constant current alternating system. This winding comprises a coil 22 and a core 23 of magnetic material. One terminal of the inductive Winding is connected by the coil of the electromagnet l0 and the conductor 19 to the upper electrode 1, while the other terminal of the winding is connected by the conductor 20 to the lower electrode 2. The inductive winding inductively interlinks the lamp circuit and the alternating current system and diverts a predetermined limited amount of energy from the system to the lamp circuit.

The inductive winding is so designed with reference to the particular kind of electrodes 1 to be used in the lamp and of the resistance of the are which they are intended to maintain, that during normal operation the magnetic circuit of the winding is far below saturation. inductive winding is, therefore, high and the magnetizing current taken by it is very small and practically negligible as compared with the current flowing between the electrodes and through the arc establishing magnet. The exciting impedance of the inductive winding is not only high but is practically constant so long as the magnetic circuit is below saturation, so that the impedance of the lamp as a whole depends essentially upon the arc resistance, and an increase of this resistance which results in an increase of the voltage at the lamp terminals will not appreciably affect the constancy of current passing through the arc and through the magnet. As now the electrodes are being consumed and the are becomes longer and its resistance higher, the current through the arc and through the magnet still remains constant, owing to the rise of potential in the system, until the point is reached when the arc has become so I long and its resistance so high that the constant current through the same is insufficient to maintain the long are stable. At this stage the difference of potential at the termin'als has so much increased that the magnetizing current taken by the inductive winding becomes sufiiciently large to saturate its magnetic circuit. As soon as this occurs the exciting impedance of the inductive winding drops very low and by far the greater amount of current now passes through the winding and thus the current through the arc is considerably reduced and The exciting impedance of the becomes too feeble to maintain the arc at all, which, therefore, collapses. The magnet 10, which up to the point of collapse of the arc was sufficiently energized to hold the arc at its normal length is denergized by the collapse and the two electrodes are again brought into contact, whereupon the arc is again established as at the start, by the clutch member 13 and its cooperating parts. This operation is repeated as often as the resistance of the arc, and thus the impedance of the lamp circuit, reaches the predetermined value and the magnetic circuit of the inductive winding becomes saturated and thus changes the inductive relation of the lamp circuit and the alternating current system.

One of the preferred forms of my invention is illustrated diagrammatically in Fig. 2. In this embodiment I inductively interlink the lamp circuit and the alternating current system by interposing in the series circuit of the alternating current system an auto-transformer. By the use of a transformer such as an auto-transformer, I am enabled to obtain the desired current value in the lamp circuit irrespective of the particular value of the current in the alternating current system. The only practical difference between the inductive devices shown in Figs. 1 and 2 is that the latter is a transformer having a ratio of transformation other than 1:1, while the former may be looked upon as representing the limiting case of a transformer and may be treated and spoken of as a transformer with a 1 :1 ratio of transformation. As far as my present invention is concerned, the ratio of transformation is entirely immaterial, and I may in fact employ an inductive device in which no transformation takes place, as is exemplified by the choke coil 23 in the arrangement shown in Fig. 1.

The conductors 17 and 1.8 of the alternating current system are connected to intermediate points of the winding of the autotransformer 36, as shown diagrammatically in Figs. 2 and 3. One terminal of the secondary circuit of the auto-transformer is electrically connected by a conductor 40 to the lower electrode 2, while the other terminal is connected by conductor 39, the coil of electromagnet '10-and conductor 19 to the upper electrode 1.

The operating mechanism of the lamp shown in Fig. 2 includes the series electromagnet 10 having the armature 11. A rod 24 is secured to the armature 11 and is bent to form a horizontal extension 24". This extension of the rod is secured to the cylinder of a dash-pot 16, the piston of which is supported by a stationary part of the lamp. A lever 25 is pivotally supported by abracket 26 and has one of its ends connected by a link 27 to the horizontal extension 24,

while its other end is provided with a counterweight 28.

The electrodes -1 and 2 are operatively supported by the arm 4, rod 3 and chain 6,

points of connection to the bracket 26 andthe link 27. The arms of the T-shaped member 30 are connected by short links 34: to

arms 31 which are pivoted to a block 32 and are provided at their adjacent ends with jaw members 33. The block 32 is apertured to receive the chain 6, which is adapted to be gripped by the jaws 33. When the block 32 engages a suitable tripping platform 35, the jaws are separated and the clutch is thus disengaged from the chain.

The auto-transformer consists of a winding having a number of turns, a to 0, arranged respectively as indicated in Figs. 2 and 3. Although I have illustrated an auto-transformer with a step-up ratio of transformation, it is obvious that this ratio may be unity or step-down as desired. The operating mechanism which I have shown in Fig. 2 can be used equally well with the lamp shown in Fig. 1, and conversely the operating mechanism shown in Fig. 1 can be used with a lamp operated from an autotransformer as shown in Fig. 2.

The lamp which I have illustrated in Fig. 2 is a constant current lamp particularly adapted for use with an electrode or electrodes containing or largely composed of titanium carbid, or metallic titanium, or a mixture of these materials, which I will hereinafter refer to as the titanium electrode. Fig. 6 of the drawings shows the curve of arc-resistance of a titanium electrode. It will be seen from this curve that the arc-resistance fluctuates greatly and accordingly the typical double peaked voltage curve of the alternating arc will have sharp irregular peaks of varying amplitude. As the electrodes are consumed the resistance of the arc increases, and, since the auto-transformer in cooperation with the generating system tends to maintain a constant current in the lamp circuit, the voltage of the arc must also increase and so the amplitude of the voltage peaks increase. The terminal voltage of the auto-transformer must also increase. The auto-transformer is so designed that its magnetic circuit becomes saturated when the arc-resistance between the electrodes causes a voltage peak of predetermined amplitude to appear in the arc.

The saturation of the magnetitc circuit of the auto-transformer determines the limit of the amount of energy which can be diverted to the lamp circuit. Below the point of saturation of the auto-transformer the current in the lamp circuit is maintained approximately constant and an increase in impedance is accompanied by an increase in voltage. When the auto-transformer becomes saturated a further increase in voltage becomes impossible, and thus a further increase in the impedance of the lamp cir cuit isaccompanied by decrease of the current. Above saturation, therefore, the voltage of the lamp circuit remains approximately constant, while the current decreases as the impedance increases. The saturation of the auto-transformer, therefore, effects a change in the inductive relation of the lamp circuit and the alternating current system. During normal operation of the lamp, the auto-transformer is operated far below saturation and it is only when a voltage peak of a predetermined value appears in the are that the magnetic circuit of the auto-transformer becomes saturated. The are voltage between the electrodes is obviously propor' tional to the arc-resistance, and the autotransformer is, therefore, so designed that it becomes saturated at a predetermined arc-resistance, being the arc-resistance at which it is desired to feed the electrodes.

The complete operation of the lamp shown in Fig. 2 will now be understood. The auto-transformer inductively interlinks the lamp circuit and the alternating current system and is adapted to divert a limited amount of energy of constant current tendency to the lamp circuit. When the lamp is not in operation and no current is flowing, the electrodes 1 and 2 are in engagement. When current is switched on, the autotransformer is energized, and as the electrodes are in engagement energy is diverted to the lamp circuit, whereby the series magnet 10 is energized and the electrodes separated a fixed distance by the operating mechanism. The dash-pot 16 retards the operating mechanism so that the electrodes are separated gradually and the are assuredly established. The are continues to burn until the resistance between the arc electrodes causes a voltage peak of such magnitude to appear as to cause saturation of the auto-transformer. The are thereupon becomes unstable and the current in the lamp circuit is interrupted and the series magnet 10 deenergized. The armature 11 falls by gravity, carrying with it the rod 24, lever 25 and clutch 29. The block 32 strikes the tripping platform 35 and the jaws 33 release the chain 6, whereby the nism, as heretofore described. This operation is repeated as often as a voltage peak.

of suflicient magnitude to saturate the autotransformer appears in the arc- Titanium electrodes are very liable to have formed 'at their arcing surface a layer of slag or other non-conducting, material which seriously interferes with the establishment of the are. My method of operation provides efficient means for overcoming this difficulty and consists in puncturing the layer of non-conducting material by high voltage impulses. The open circuit reactions of an auto-transformer, particularly well adapted for carrying out my method of operating an arc lamp, are shown graphically in Fig. 5. Here the sinoidal curve 2' represents the primary current, a the -magnetic flux, and .o the induced secondary voltage, all on open circuit. The magnetic circuit of the auto-transformer becomes saturated when the current wave attains the value indicated by a. The change in flux density, therefore, occurs between the points a above the neutral line and the next adjacent point a below the neutral line. During the remaining part of the current wave the flux is practically constant. The induced voltage is produced-by the change in flux, and while \the flux is practically constant, the induced voltage is practically zero. The induced voltage curve, therefore, takes the form indicated in Fig. 5 by a). While the effective or root mean square value of the voltage induced by tlr fiat topped flux wave cp is somewhat greater than that induced by a sinoidal flux wave of the same maximum value, the maximum value of the voltage induced by the flat topped wave is very much greater and much higher still than that which would be given by a sinoidal wave of the same effective value. The voltage wave induced by the fiat topped flux wave therefore consists of a series of high voltage impulses as indicated bythe curve 42. These high voltageimpulses .are of such magnitude as to establish conduction through the non-conducting or poorly conducting material at the arcing surface of the electrodes so that the arc is established.

In Fig. 4 I have shown a lamp which has the same general arrangement as shown in Figs. 1 and 2. Energy is diverted to the lamp circuit by the operation of the auto-transformer 36, as in Fig. 2. The

movement of the armature 11 of the series nected to the clutch member by means of a rod 12. The rod is provided with an arm 41 which carries a movable sprung-supported contact 42 cooperating with a stationary contact 43. The movable contact 42 is electrically connected to conductor 19, while the stationary contact is connected to one terminal of the coil of an auxiliary electromagnet 44. The other terminal of the coil of this magnet is connected to the conductor 39. I The magnet 44 has a pivoted armature 45 whose movement in one direction is limited by a pin 45. The armature cooperates with a detent 46 on the rod 12 to hold the armature 11 elevated when the magnet44 is energized. The object of the auxiliary magnet 44 is to avoid the drop of potential across the series magnet 11 during the normal operation of the lamp. The magnet 10 is energized and the arc established in the manner heretofore described. The movement of 'the rod 12 brings the contacts 42' and 43 into engagement, thereby establishing a circuit in shunt relation to the series magnet 10 through the coil of the auxiliary magnet 44. The armature 45 is attracted by the energized magnet 44 and cooperates with the detent 46 to support the armature 11. The magnet 44 is designed to consume less energy than the magnet 10 and accordingly the shunting of the latter magnet by the former effects a saving in the energy consumedin the lamp circuit. V

The operation of the lamp shown in Fig. 4 is the same as heretofore explained. The

saturation of the magnetic circuit of the auto-transformer 36 occurs at a predetermined voltage peak, and the greater amount of the current is by-pathed through the primary winding. The electromagnet 44 is thereby deenergized and releases the clutch member 13 so that the electrodes 1 and 2 can come into engagement by gravity. The engagement of the electrodes completes the lamp circuit and the magnet 10 becomes energized and raises its armature 11 a fixed distance. The contacts 42 and 43 are brought into engagement and the electromagnet 44 energized, thereby shuntlng the coil of the magnet 10 and raising the armature 45 into engagement with detent 46..

I have illustrated an auto-transformer having a ratio of transformation of about 1 to 2, or, to be more exact, 2.8 to 6.6. I have built a lamp using such 'an auto-transformer in conjunction with a lower electrode made of a thin metal tube filled with a mixture comprising titanium carbid 96 parts, copper oxid 3 parts, and lithium fluorid 1 part, and a plain carbon as the upper electrode. With electrodes of this character, I find that the arc may be advantageously operated with a current ofabout 2.8 amperes from a' standard 6.6 ampere series alternating current system. With an autotransformer constructed for such transformation, I have. found it possible to impress upon the electrodes voltage impulses of 1000 volts or more when the electrodes are in engagement and before the arc is started, without injury to the lamp.

While I have illustrated and described in connection with Figs. 2 and 4 of the drawings an auto-transformer having a step-up ratio of transformation, it is obvious that my invention is in no sense limited to such an arrangement. The ratio of transformation may be step-down or may be unity. In the latter case the auto-transformer may take the form of a simple inductive winding, which may be a choke coil, interposed in the alternating current system with the lamp circuit connected in shunt thereto, as illustrated in Fig. 1. It is furthermore obvious that an ordinary series transformer may be used instead of an auto-transformer.

I have, therefore, employed in the appended claims the expression inductive device to cover broadly any inductlve means for d1- verting electr1c energy to the lamp c1rcu1t.

Such inductive device will be designed, with reference to the electrodes which are employed and the character of the are produced thereby, to become magnetically saturated at those periods when the condition of the arc makes feeding of the electrodes desirable.

It is obvious that my invention enables me to make use of an arc lamp mechanism that is exceedingly simple, since a single operating magnet and a single clutch is all that is necessary for the successful operation of the lamp. The series magnet thus directly actuates the feeding mechanism of the electrodes. As previously mentioned, my method of operating arc lamps is particularly suitable where titanium electrodes are employed, producing an arc whose voltage is irregular and peaked. I have found with such an arcthat it is desirable to feed the electrodes at intervals of from twenty to thirty minutes. The interval of feeding will obviously depend upon the arc under consideration, and may vary over a wide.

range in the case of arcs of difi'erent characters, and I do not, therefore, desire to limit my invention to any particular time interval for feeding of the electrodes. The inductive device interlinking the lamp circuit and the alternating current system is designed to effect the feeding of the electrodes by its magnetic reaction, when the condition of the arc makes feeding desirable. My method of operation does not rely upon abnormal phenomena occurring with some arcs by a change of electrodes, as rectification, but depends solely on the normal operating condition of the alternating arc. With my method of operation, the voltage and current are always alternating, the terminals always the same arcing terminals, and the arc voltage curve always the same double peaked voltage'waves with the two peaks of varying height. The inductive device is designed so as to give a saturation voltage within the range covered by the variations. of the peaks of the normal alternating arc voltage wave, that is, within the range of normal operating voltage variations. v

Itwill be understood that an economizer will be used and that stops will be employed for limiting the movement of the clutch so that an arc of a predetermined length will be established. Those features, however, and other features which are common and well known in the flame arc lamps and luminous arc lamps have not been shown, in order to simplify the illustration.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The method of starting an alternating current are lamp, having an insulating film between the contacting electrodes, which consists in so distorting the voltage wave from an inductive device, which diverts the normal working current to the lamp, as to impress upon the arc electrodes voltage impulses sufficiently high to puncture the insulating film and thereby start the normal current to establish the are.

2. The method of starting an alternating current are lamp having an insulating film between the contacting electrodes, which consists in distorting the voltage wave from an inductive device which diverts the work ing current to the lamp prior to the establishing of the arc, in such a way as to impress upon the arc electrodes high voltage impulses adapted to puncture the film of insulating material on the arcing surfaces of the electrodes.

3. The method of establishing an arc in an alternating current are lamp having an insulating film between its contacting electrodes, which consists in impressing upon the arc electrodes a series of high voltage impulses from an inductive device which is adapted to have its point of magnetic saturation passed at each alternation of the inducing current.

4:. An alternating current are lamp in which the electrodes are in contact when the lamp is not working, one or both electrodes being of a material apt to form an insulating film at the arcing surface and thereby open-circuit the lamp when the electrodes are in contact, in combination with a local auto-transformer adapted to divert a normal working'current to the lamp, from a constant current system, said transformer being constructed to become magnetically saturated when the arc resistance abnormally rises, whereby it diverts from the arc circuit the energy required to sustain the higher resistance arc and passes high voltage dischargesbetween 'the'electrodes when they are in contact through the insulating film to puncture the film for the passage of the normal working current.

5. An alternating current arc lamp having an electrode which is apt to form an insulating film at its arcing surface and thus opencircuit the lamp when the electrodes are in contact, in combination with a local autotransformer adapted to divert the normal Working current to the lamp from a constant current system, said transformer being constructed to become magnetically saturated when the arc resistance abnormally rises and thereby divert from the arc circuit the energy required to sustain the high resistance are and to pass high voltage discharges between the electrodes when they are separated by an insulating film, whereby such film is punctured for the passage of the normal working current.

6. An alternating current are lamp whose electrodes are in contact when the lamp isnot working, in combination with an electroresponsive means in series with the electrodes adapted when energized to separate the electrodes a definite distance to establish the arc and to hold the electrodes in the new position while it is energized, and a local inductive device for diverting from a constant current system to the lamp circuit a limited amount of energy sufiicient to sustain a normal arc and to keep the electro-responsive means energized, said inductive devicebeing constructed to become magnetically saturated and thereby absorb from the system and prevent access to the electrode circuit the increased energy required to sustain the arc when the resistance of the latter abnormally increases, whereby, upon such increase, the arc iscaused to collapse, the electro-responsive means to become deenergized and the electrodes to come into contact.

7 The method of operating an alternating current are lamp having electrodes whose arc resistance fluctuates over a wide range and whose voltage is accordingly irregular and peaked, which consists in diverting to the lamp circuit a limited amount of energy of constant current tendency from an inductive device, separating the electrodes a fixed distance, causing the inductive device to become magneticallysaturated when an abnormal high voltage peak appears in the arc, and thereby preventing the access to the arc of the increased energy required to sustain it and causing it to collapse.

In witness whereof, l have hereunto set my hand this 2nd day of October, 1912.

CHARLES P. STEINMETZ.

Witnesses:

BENJAMIN B. HULL, MARGARET E. WOOLLEY. 

